Just finished the valve check at 3,000 miles, since I don't know if the previous owner did the 600 mile check. All were within spec. Today, when reinstalling the air box, I accidentally actually read the section in the manual which stated to check the O-rings for damage. Sure enough ... one appeared to have been cut completely through, creating a gap. Maybe it was a glue joint that separated, since it has been mentioned that the O-ring is made of tubing glued end-to-end. I noted the squishy nature of the material and, although I could see the logic of such a material in the application, it doesn't seem to be a very durable material. Sort of like those grey foam loudspeaker driver surrounds that start to rot as soon as they are manufactured. I grabbed my large Storehouse assortment of rubber O-rings which can be had from Harbor Freight for maybe $10 for perhaps a couple hundred O-rings in assorted sizes. The largest size fit right into the groove in the air cleaner housing. The firmer composition didn't seem to matter when the funnel screws were tightened. Cheap, Chinese rubber O-ring assortment to the the rescue again!